Instability of cosmological event horizons of non-static global cosmic strings

TL;DR

This paper investigates the stability of cosmological event horizons associated with non-static global cosmic strings, demonstrating that they are unstable and tend to develop into singularities under perturbations.

Contribution

It provides the first detailed analysis showing that these horizons are unstable to both test particles and physical perturbations, leading to singularities.

Findings

Cosmological event horizons are unstable to perturbations.

Perturbations cause horizons to evolve into strong singularities.

Back reaction of null dust perturbations results in spacetime singularities.

Abstract

The stability of the cosmological event horizons found recently by Gregory [Phys. Rev. D54, 4955 (1996)] for a class of non-static global cosmic strings is studied. It is shown that they are not stable to both test particles and physical perturbations. In particular, the back reaction of the perturbations of null dust fluids will turn them into spacetime singularities. The resulted singularities are strong in the sense that the distortion of test particles diverges logarithmically when these singular hypersurfaces are approaching.